Yanping Chen and Tianliang Hou. (2012). Superconvergence and $L^{\infty}$-Error Estimates of RT1 Mixed Methods for Semilinear Elliptic Control Problems with an Integral Constraint. Numerical Mathematics: Theory, Methods and Applications. 5 (3). 423-446. doi:10.4208/nmtma.2012.m1118